The best diet is the healthiest one you can stick to Original paper

In this secondary analysis of a diet trial, participants experienced greater weight loss and improved health markers if they had both higher diet adherence and higher diet quality, regardless of whether they ate a low-carbohydrate or low-fat diet.

Whether higher diet adherence and diet quality is associated with greater weight loss and improved health markers in the context of low-carbohydrate and low-fat diets.

The primary outcome was BMI. The secondary outcomes were systolic and diastolic blood pressure, fasting glucose, insulin, triglycerides, HDL-C, and LDL-C.

448 participants (average age of 40; 258 women, 190 men) with a BMI of 28 to 40.

This was a secondary, observational analysis of a 1-year randomized controlled trial. In the original trial, the participants were assigned to follow either a low-carbohydrate or low-fat diet, with both diets designed to be generally healthy (by emphasizing vegetables and other whole foods and minimizing sugar, refined flours, and trans fat). In this secondary analysis, the investigators examined whether diet adherence and diet quality, alone and in combination, were associated with improvements in various markers of cardiometabolic health in both diet groups.

Diet adherence was defined differently in the 2 diet groups. For the low-carbohydrate group, higher diet adherence was defined as reducing daily carbohydrate intake by at least 103.2 grams. For the low-fat group, higher diet adherence was defined as reducing daily fat intake by at least 29.7 grams.

Diet quality was defined according to the Healthy Eating Index-2010 (HEI). In short, a higher HEI score involves consuming higher amounts of fruits, vegetables, greens and beans, whole grains, dairy, total protein foods, seafood and plant proteins, a higher ratio of unsaturated to saturated fat, and lower amounts of refined grains, sodium, and empty calories (e.g., alcohol and refined sugar). Higher diet quality was defined as having an HEI score higher than the median for one’s assigned diet group.

The analyses were adjusted for potential confounders, including age, sex, and baseline body weight.

In both diet groups, BMI decreased more in participants with higher diet adherence and higher diet quality than in participants with lower diet adherence and lower diet quality.

Participants with higher diet adherence and higher diet quality also experienced reductions (improvements) in systolic and diastolic blood pressure (both diet groups), fasting glucose and insulin (low-carbohydrate group only), and LDL-C (low-fat group only) compared to participants with lower diet adherence and lower diet quality.

For most outcomes, having either higher adherence or higher diet quality appeared beneficial, but not as much as having both, suggesting that diet adherence and diet quality were both important factors. This means that eating the highest quality food in a regimen you can adhere to is more important than whether you eat a low-carbohydrate or a low-fat diet.